Is it cheaper to do the research before you start building a bunch of units or build the units and then research and upgrade to a higher level?
For example, is it cheaper to build a bunch of level 1 planes and then do the research and upgrade them to level 3 or cheaper to research up to level 3 and then build level 3 planes?
For example, is it cheaper to build a bunch of level 1 planes and then do the research and upgrade them to level 3 or cheaper to research up to level 3 and then build level 3 planes?